WASHINGTON — Lawmakers from both parties lashed out at the newly appointed director of the Secret Service at a hearing Tuesday, accusing him of doing little to restore the public’s faith in an agency jolted by embarrassing scandals and security breaches.

Republican lawmakers seized on accusations that two drunken Secret Service agents crashed a government car into a White House barricade after a party this month. Representative Harold Rogers, Republican of Kentucky and the chairman of the House Appropriations Committee, called the incident “unacceptable” and said it represented a “breakdown, to put it mildly, of the discipline within the ranks of your agency.”

Democratic members were no less critical. Representative Nita M. Lowey of New York, the ranking Democrat on the committee, urged the agency’s director, Joseph P. Clancy, who took over last month, to demand discipline. She repeatedly pressed him to fire the agents in question, saying their actions proved they were “not the kind of person” that should be employed to protect the president.

Under aggressive questioning, Mr. Clancy cautioned that some of the facts about the March 4 accident had not been verified. Contrary to initial reports of a dramatic crash into a White House barricade, Mr. Clancy said, a surveillance video showed the agents’ car slowly nudging an orange construction barrel out of the way so it could move forward.

But during the two-hour hearing before the committee, Mr. Clancy seemed nervous and hesitant, and he conceded that lawmakers were right to be angry about the actions of the agents. He offered no other details, emphasizing that an investigation was being conducted by the inspector general of the Department of Homeland Security, which oversees the Secret Service.

“I am very eager to hear the results of this investigation,” Mr. Clancy told the lawmakers. “I don’t know how long it will take, but I am committed to due process.” He acknowledged that the incident would be the first test of his leadership.

He said he did not know whether the two agents had been intoxicated because no test had been conducted. He said he had not talked to any of the officers at the scene or their supervisors to avoid the perception that he was putting pressure on them. And he said federal rules about hiring and firing restricted his ability to discipline the men until the investigation was completed.

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Some background on the chain of mistakes at the Secret Service and the importance of leadership as the agency tries to get past its difficult stretch.Published OnNov. 13, 2014CreditImage by Doug Mills/The New York Times

“I’m frustrated that I can’t act until we get all the facts,” Mr. Clancy told the members of the committee. He added: “I just want to respect the due process, as frustrating as that is, and then let my actions speak for how we’re going to move forward in this agency.”

Mr. Clancy said he was disturbed that he did not learn of the episode until five days after it happened, after an anonymous email sent from a whistle-blower at the Secret Service to people inside the agency. Mr. Clancy said he had told the agency’s officials that there was “no excuse” for the delay in reporting the event.

“We had a good, stern talk about that,” Mr. Clancy told the lawmakers.

Lawmakers at the hearing said they were stunned that Mr. Clancy had initially been kept in the dark, and they urged him to hold other officials accountable for what they said looked like an effort to protect their colleagues.

Mr. Clancy succeeded Julia A. Pierson, who resigned under pressure after a fence-jumper made his way deep into the White House residence. Mr. Clancy’s appearance before the committee, to review the agency’s 2016 budget request, had been scheduled before the latest scandal became public.

Critics of the agency said Mr. Clancy was already failing to fix a culture that encourages poor behavior by employees. In 2012, a dozen Secret Service agents were caught with prostitutes in Cartagena, Colombia. On a presidential trip to Europe last year, an agent was found passed out in a hotel hallway after a night of drinking.

There are still many questions about what exactly happened in the latest blunder at the White House. Many agents and officers had apparently attended a going-away party for the agency’s spokesman at a Washington bar. Mr. Clancy acknowledged that some of his agency’s employees turned to alcohol to deal with their stressful jobs.

“There is an element within our agency that does cope with the stresses that many of you have mentioned today by using alcohol,” he said, though he added that others dealt with stress by exercising, turning to religion or spending time with their families.

“People know the rules,” he said. “It’s up to individuals to have the self-discipline.”

Mr. Clancy said the two agents had been reassigned to nonsupervisory positions while the investigation was conducted, a standard practice in such inquiries. But lawmakers said they were not satisfied with those actions.

“This is the last in a long line of episodes, somewhat similar, drinking, carousing on and off duty,” Mr. Rogers said, adding, “We’ve got to have some changes, and you’ve got to be the one to make those changes.”

Mr. Rogers pledged to keep the Secret Service on a “short string” after the recent scandals and security lapses. He said the missteps “will not stand.”

Ms. Lowey said the recent incident at the White House “raised serious questions about its ability to protect the president.”

In his testimony, Mr. Clancy urged lawmakers to approve a 16.4 percent increase in the Secret Service budget to confront staffing, training, facility and infrastructure shortcomings that he says helped lead to the problems. Mr. Obama’s budget for 2016 asks for $1.94 billion, an increase of $273.3 million over the current year.

The Secret Service budget request is intended to challenge lawmakers, and especially Republicans, to back up their vocal criticism of the agency with federal money to make changes.

The request includes $3.4 million to address attrition in the ranks of Secret Service officers who patrol the grounds and perimeter of the White House. It includes funding for upgrades to radio communications at the White House as well as $8.2 million for a two-year project to construct a taller fence around the White House grounds.

Mr. Clancy said that a new fence would take at least a year and a half to finish, but that the agency was working on temporary measures, such as modifying the top of the existing fence, that could be in place by summer.

“We recognize that’s a long time to wait, a year and a half,” he said.

A version of this article appears in print on , on Page A17 of the New York edition with the headline: Secret Service Chief Chastised by House Panel After Agents’ Latest Lapse. Order Reprints | Today’s Paper | Subscribe